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81.
Nematodes have difficult control and complex handling, but considering the physiological and biochemical changes that micronutrients promoting in plants, there is possibility that the supply with these chemicals increases the resistance of plants against nematodes. Thus, the present study aimed to assess the effect of the application of boron and zinc on the reproduction of Meloidogyne incognita, embryonic development and juvenile nematode hatching. Nematode reproduction was evaluated in tomato plant inoculated with 2000 eggs and treated in the aerial part with boron or zinc at the following doses: 0, 1/2, 1×, 2× and 4× the manufacturer's recommendation (100 and 30?g/L, respectively), with the plants assessed 60 days after inoculation. For assessment of embryonic development and juvenile hatching, 1?mL nematode suspension was placed in Petri dishes containing 9?mL of the same doses of boron and zinc, and assessment occurred four and eight days after incubation. Results obtained showed that boron controlled nematode population at the dose of 400?g/L and promoted juvenile hatching when used at maximum dosage on the eighth day. Zinc reduced the number of galls and the number of eggs at the dose of 60?g/L, but did not exhibit direct effect on nematode.  相似文献   
82.
The aim of this study was to assess the effect of different supplements on the behavior variables of crossbred dairy cows that were in pasture that comprised two 4?×?4 Latin squares (four periods, four treatments, and four animals). Each experimental period lasted 15 days (10 days to adapt animals to treatments and 5 days for data collection). The animals were supplemented twice a day, with different forage (corn silage and cactus pear) and concentrate sources (soy mea + wheat meal + corn meal + cotton seed together and soy meal as a single constituent of the concentrate). A significant difference (p?<?0.10) was observed for the percentage of time spent consuming the supplement and for idleness, rumination, and bite rate at the time of supplementation. The supplement intake period was greater for the cactus pear-based supplements due to the lower dry matter content. Those based on corn silage resulted in longer rumination periods than those consisting of cactus pear; however, the opposite was observed for supplements based on the cactus, which showed higher percentages of time for idleness. The supplementation influenced the ingestive behavior of crossbred dairy cows.  相似文献   
83.
RNA-based disease control has shown great potential for controlling pest and diseases in crop plants. While delivery of inhibitory noncoding double-stranded (ds)RNA by transgenic expression is a promising concept, it requires the generation of transgenic crop plants, which may cause substantial delay for application strategies depending on the transformability and genetic stability of the crop plant species. Focusing on agronomic important barley - Fusarium spec. pathosystems, we have sought for alternative strategies to apply dsRNAs for fungal control. Recently, we have demonstrated that a spray application of a long noncoding dsRNA termed CYP3RNA, which targets the three fungal Cytochrome P450 lanosterol C-14α-demethylase genes FgCYP51A, FgCYP51B, and FgCYP51C, inhibits Fusarium graminearum (Fg) on barley leaves (Koch et al., PLoS Pathogens, 12, e1005901, 2016). Here we show that another Fusarium species, F. culmorum (Fc), also is sensitive to CYP51-derived dsRNAs. Treating Fc with various dsRNAs targeting the genes FcCYP51A, FcCYP51B and FcCYP51C was destructive to the fungus and resulted in growth retardation in in vitro cultures. We discuss important consequences of this finding on future RNA-based disease control strategies. Given the ease of design, high specificity, and applicability to diverse pathogens, the use of target-specific dsRNA as an anti-fungal agent offers unprecedented potential for novel plant protection strategies.  相似文献   
84.
The current study aimed to evaluate the effect of top-dressed potassium (K) application on the production of hybrid cucumber “Sapphire.” The experimental design was a randomized complete block, with five blocks of 0.80 × 0.40 m2 each and eight replicate plants per block. The five fertilization rates of K used were 0, 45, 90, 135, and 180 kg K2O ha?1. Data collection consisted of the estimation of fruit diameter, fruits length, fruit fresh and dry weights, the number of fruits per plant, and the weight of fruits per plant. The number of fruits per hectare and the fruit fresh weight per hectare were calculated. Fruit tissue was analyzed for determination of macronutrient concentrations, pH, titratable acidity, soluble solids, sugar contents, and protein content. The data were statistically analyzed using regression analysis and analysis of variance (ANOVA). There was a significant effect of the fertilization rate of K on fruit diameter, fruit fresh and dry weights, macronutrients concentrations in fruits, titratable acidity, soluble solids, and reducing sugars. A quadratic equation was adjusted for the number of fruits per plant and per hectare; fruit yield per plant and per hectare, with maximum top-dressing doses, was estimated to be between 60 and 95 kg K2O ha?1. A linear increase was obtained in the pH. An increase in the K fertilization rate caused a linear decrease in the fruit length.  相似文献   
85.
Thiamethoxam (TMX) is one of the most widely used neonicotinoid insecticides for pest control in agricultural crops. However, information on its acute and chronic toxicity for freshwater non-target insects is still limited. We aimed to evaluate the lethal and sub-lethal effects of TMX-based insecticide on Chironomus xanthus using laboratory ecotoxicological assays. Besides survival, 28-day partial life-cycle tests assessed the effects of chronic exposures on larval growth and emergence of midges. The estimated 48-h LC50 was 32 μg a. i./L of TMX. Chronic tests revealed that chironomids exposed to sub-lethal concentrations of TMX showed reduced larval growth (LOEC?=?0.4 and 1.6 μg a.i/L of TMX for head capsule width and growth rate, respectively) and emergence rate (LOEC of 1.6 μg a.i/L of TMX). This study provides important ecotoxicological data concerning effects of TMX-based insecticides on tropical ecosystems and reveals that environmentally relevant concentrations of TMX can adversely affect chironomids populations. Our study also validates C. xanthus as a sensitive species to monitor the ecological integrity of tropical aquatic systems near intensive agricultural areas and to help understand the effects caused by TMX on freshwater insects.  相似文献   
86.
The present study was conducted to evaluate the effects of high and low supplementation levels pre- and post-weaning on performance, endocrine, metabolic, and reproductive responses of Nellore heifers. Fifty Nellore heifers with 132?±?9.9 kg average body weight (BW) and 138?±?19 days of age were supplemented from 4 to 14 months. The heifers were distributed into five supplementation plans: HH—6 g/kg of BW of supplement pre- and post-weaning, HL—6 g/kg of BW of supplement pre-weaning and 3 g/kg post-weaning, LH—3 g/kg of BW pre-weaning and 6 g/kg of BW post-weaning, LL—3 g/kg of BW pre- and post-weaning, and CC—control, no supplementation. Interactions were not significant (P?>?0.10). The level of supplement fed pre-weaning did not affect any of the performance variables evaluated at the end of the experiment (P?>?0.10). There was a significant effect of supplementation and level of supplementation fed post-weaning on average daily gain (ADG) and final BW (P?<?0.05). Overall ADG was also affected only by supplementation and level of supplement fed post-weaning (P?<?0.05) with animals receiving 6 g/kg of BW post-weaning gaining more weight. Follicular diameter was greater in animals that received 6 g/kg of BW post-weaning (P?<?0.05). In summary, performance, endocrine, metabolic, and reproductive variables evaluated in the current study were improved by the level of supplement fed post-weaning. Heifers receiving supplementation of 6 g/kg of BW post-weaning had greater responses, independent of the level received during the pre-weaning phase.  相似文献   
87.
The aims of the present study were to determine (i) the profiles of phylogroup and (ii) the antimicrobial susceptibility of pathogenic Escherichia coli strains isolated from calves, and of Salmonella spp. strains isolated from calves and pigs in Minas Gerais State, Brazil. Sixty-one pathogenic E. coli strains and Salmonella spp. (n?=?24) strains isolated from fecal samples of calves and Salmonella spp. (n?=?39) strains previously isolated from fecal samples of growing/finishing pigs were tested. The minimum inhibitory concentration (MIC) using the agar dilution method was determined for nalidixic acid, amikacin, amoxicillin, ampicillin, cefoxitin, norfloxacin, gentamicin, tetracycline, and trimethoprim-sulfamethoxazole. All E. coli isolates were susceptible to amikacin. Tetracycline was the antimicrobial that presented the higher frequency of resistance among E. coli strains, followed by ampicillin, trimethoprim-sulfamethoxazole, amoxicillin, nalidixic acid, norfloxacin, gentamicin, and cefoxitin. E. coli (n?=?61) strains isolated from calves belonged to different phylogroup namely, phylogroup A (n?=?26), phylogroup B1 (n?=?31), phylogroup E (n?=?3), and phylogroup F (n?=?1). Phylogroups B2, C, and D were not identified among the E. coli in the present study. All Salmonella spp. (n?=?24) strains isolated from fecal samples of calves were susceptible to amikacin, amoxicillin, ampicillin, norfloxacin, gentamicin, tetracycline, and trimethoprim-sulfamethoxazole. Resistance to nalidixic acid and cefoxitin was detected in 16.66 and 8.33 % of the Salmonella spp. strains, respectively. Among the Salmonella spp. (n?=?39) strains isolated from fecal samples of pigs, the higher frequency of resistance was observed to tetracycline, followed by amoxicillin, gentamicin, ampicillin, trimethoprim-sulfamethoxazole, nalidixic acid, cefoxitin, and norfloxacin. All strains were susceptible to amikacin. Forty-eight (78.68 %) of the E. coli strains were classified as multidrug-resistant, whereas among Salmonella spp. strains, the percentage of multidrug resistance was 57.14 %, being all multidrug-resistant strains isolated from pigs (92.30 %). The results from the present study indicate a high frequency of antimicrobial resistance among pathogenic E. coli strains isolated from calves and Salmonella spp. strains isolated from pigs and a high rate of susceptibility to most antimicrobials tested among Salmonella spp. strains isolated from calves. Our study highlights the presence of multidrug-resistant strains of E. coli and Salmonella spp. isolated from food-producing animals in Minas Gerais, Brazil.  相似文献   
88.
Effects of ethanol and nitrate on linear alkyl benzene sulfonate (LAS) degradation were investigated using central composite design. At experimental design, removal of 99.9% was observed in batch reactors (1 L) with 9.8 to 41.2 mg L?1 of LAS. The batch reactors were kept under agitation at 120 rpm and 30 °C. Ethanol (co-substrate) and nitrate (electron acceptor) were statistically significant factors (p?<?0.05) in surfactant removal. Optimal values were 97.5 and 88 mg L?1 for ethanol and nitrate, respectively. LAS removal was kinetically investigated by varying surfactant concentration while using optimal values. Batch I (27 mg L?1 LAS) exhibited greater degradation rate (KLAS) (0.054 h?1) in the presence of ethanol and nitrate. Nonetheless, in Batch II (60 mg L?1 LAS), the KLAS values decreased in those reactors probably due to inhibition by excess substrate for same concentrations of nitrate and ethanol added in reactors. As LAS concentration increased, the dominance of bacterial populations also increased, whereas diversity index decreased from 2.8 (inoculum) to 2.4 and 2.5 for reactors with both added nitrate and ethanol and those with only added ethanol, respectively. Probably, a selection of microbial populations occurred in relation to LAS concentration. The nitrate and ethanol, at able concentration, made it possible the induction of denitrifying microrganisms foward to LAS removal.  相似文献   
89.
Oil spills might lead to severe environmental impacts to the affected fauna, disrupting local food webs, and causing mass mortality in many species. However, little is known about long-term impacts of oil spills, or even if such impacts can be detectable after several generations. In this study, we investigate the genetic variability of three freshwater species—Mimagoniates microlepis (Characiformes: Characidae), Scleromystax barbatus (Siluriformes: Callichthyidae), and Phalloceros harpagos (Cyprinodontiformes: Poeciliidae)—in rivers that were affected by a large oil spill in the state of Paraná, southern Brazil, on February of 2001. Samples were obtained from nine different locations, such that rivers that were directly affected by the oil spill could be compared with similar rivers in the same region that were unaffected. A fragment of the cytochrome C oxidase subunit I mitochondrial gene was sequenced from each specimen, and the level of genetic variability was assessed. Based on estimates of haplotype and nucleotide diversity, no impact of the oil spill could be detected in impacted rivers. These results suggest that fish populations in the region showed resilience to the pollutant, such that immigration from other locations was able to reestablish levels of genetic variability comparable to those of unimpacted rivers.  相似文献   
90.

The animal and its environment make up an integrated system, where each acts on the other. Tropical regions are characterized by high levels of solar radiation and environmental temperature which may adversely affect animal production. This study carries out a multivariate analysis of physical and physiological traits in sheep in the Federal District of Brazil to test the ability to separate groups of animals and determine which traits are most important in the adaptation of animal to heat stress. The variables studied included coat thickness, number and length of hairs, pigmentation of the skin and coat, number of sweat glands as well as heart and respiratory rates, rectal and skin temperatures, sweating rate, and blood parameters. Five groups of ten animals were used depending on breed (Bergamasca, crossbred, or Santa Inês) or coat color (Santa Inês—brown, white, and black). The data underwent multivariate statistical analyses including cluster, discriminate, and canonical, using Statistical Analysis System—SAS®. The tree diagram showed clear distances between groups studied and canonical analysis was able to separate individuals in groups, especially Bergamasca and white Santa Inês. The canonical correlation redundancy analysis showed that coat reflectance as well as hair length and number of hairs per unit area were the most useful in explaining changes in physiological traits. Skin and coat traits such as hair length, coat reflectance, percentage of epithelial area occupied by sweat glands, skin reflectance and thickness, as well as heart and breathing rates were the most important in separating these groups.

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